It is proposed with the methods available for preparing different plasma membrane fractions of gastric mucosa to (a) establish the cellular and cellular surface origin of these membranes, (b) continue investigation of enzymic and transport properties of these fractions, (c) determine the relationship of Ca ions and cAMP dependent phosphokinase in these fraction and (d) to continue to study incorporation of these membranes into planar bilayers, especially those containing H ion plus K ion ATPase.